Field
The disclosure relates to a tire tread for a civil engineering vehicle (of “off-road” type), this tread having a tread pattern capable of clearing earth better while at the same time maintaining good properties of grip and wear.
Of the uses to which civil engineering tires are put, a notable distinction is made of the use to which articulated dump truck tires are put. This use is very specific because it requires the vehicles to have a good ability to cover soft and uneven terrain.
Description of Related Art
Usually, a tire intended to be fitted to a civil engineering vehicle is provided with a tread surmounting radially on the outside a crown reinforcement which itself surmounts a carcass reinforcement. This tread has a tread pattern formed of raised elements (ribs or blocks) these raised elements being delimited by a plurality of grooves.
The raised elements of the tread have faces—referred to as contact faces—radially on the outside of the tread, which are intended to come into contact with the ground. The grooves have depths at most equal to the thickness of the tread and have geometries, when viewed in cross section, suited to limiting the retention of stones and other objects present on the ground and which may become trapped in the said grooves.
When driving over soft ground (soil, mud), the grooves fill with soil and this may prove detrimental to traction. It is therefore necessary for these grooves having become filled when they form the contact patch to be able to be rid of this soil so that they exhibit suitable grip and traction. What happens is that the grooves remain filled with soil as they next form the contact patch so that it becomes difficult to bite into the ground again in order to develop traction. The traction of the vehicle is thereby reduced in consequence.
One solution to this problem has already been implemented on tires intended notably to run on soft ground. With this solution, a tire comprises a tread provided with a plurality of grooves of circumferential and transverse orientation, these grooves delimiting a plurality of blocks among which can be distinguished two rows of blocks that form the edges of the tread, these rows being axially furthest towards the outside on each side of the tread. This solution involves offsetting one of the lateral faces of one block in two of the edge rows of blocks axially inwards. By thus creating a space axially on the outside of one edge block it has been found that it is possible to eject the soil that may have entered the grooves in the contact patch in which the groove is in contact with the ground on which the tire is being driven.
This solution, effective though it may be, still has a limit on grip and traction because it reduces the length of entry edge corner in the contact patch of one block in two.
The object of embodiments of the invention is to propose a solution to the problem that has just been outlined, namely to produce a tread pattern for a tire of a civil engineering vehicle of the articulated dump truck type, for which the ability to clear the mud or soil trapped in the transverse grooves between the blocks of the edge rows is improved, without however disturbing the longitudinal grip and traction of the vehicle.